Traceability links between issues and commits record valuable information about the evolutionary history of software projects. Unfortunately, these links are often missing. While deep learning stands as the current state-of-the-art (SOTA) in automated traceability link recovery (TLR), its effectiveness is faced with the practical problem of limited labeled data during training. To overcome this challenge, in this paper, we propose DSSLink, a novel method based on deep semi-supervised learning, enhancing deep-learning-based link recovery tasks. DSSLink first learns knowledge from labeled data through pre-trained model and then leverages deep semi-supervised learning to infer pseudo-labels on unlabeled data. The extended dataset of pseudo-labeled and labeled data re-trains the deep learning model in an iterative process. Our extensive evaluations are conducted on two SOTA traceability methods (T-BERT and BTLink) across four GitHub projects and 11 Apache projects. Specifically, the maximum F1-score improvements for GitHub and Apache projects reached 22.9% and 43.5%, respectively. Evaluation results show that DSSLink is effective in enhancing TLR performance and outperforms TraceFUN, a recent approach that utilizes unlabeled data for TLR. The source code of DSSLink is available at https://github.com/DSSLink.